.focus{
    width: 500px;
    height: 300px;
    margin: 50px auto;
    position: relative;
}

.focus img{
    width: 100%;
    height: 300px;
}

.focus .btn{
    position: absolute;
    top: 140px;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background: rgba(0, 0, 0, 0.4);
    text-align: center;
    line-height:30px ;
    color: white;
    font-size: 16px;
    font-family: '宋体';
}

.focus .btn:hover{
    cursor: pointer;
    background: rgba(0, 0, 0, 0.9);
}

.focus .prev{
    left: 0;
}

.focus .next{
    right: 0;
}

